CN101055285A

CN101055285A - Voltage measuring instrument with minimum stepping 0.1uV

Info

Publication number: CN101055285A
Application number: CN 200710068927
Authority: CN
Inventors: 张春雷; 方李
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-29
Filing date: 2007-05-29
Publication date: 2007-10-17
Anticipated expiration: 2027-05-29
Also published as: CN100529768C

Abstract

A voltage measuring instrument with the minimum stepping reaching 0.1 muV includes a first stepping panel composed of a measuring panel and two bracket panels without welding resistance, a second stepping panel comprising a measuring panel formed of a 9x9 ohm ring resistance meshwork and two 1 ohm resistance, a bracket panel formed by a ten 0.5 ohm resistances, a third stepping panel comprising of a measuring panel of 10x1 ohm and a substitution panel. Each contact of the forth stepping panel is connected with the corresponding contact of the measuring panel of the third stepping panel, and two resistances of 100 ohm are used to shunt current for range conversion at x1, x0.1 range with the minimum resolution reaching 0.1 muV, the measuring panels are connected by conductors without on-off switch, which is capable of ignoring variation and potential effect when measuring by voltage measuring instrument.

Description

A kind of minimum step is the voltage-measuring equipment of 0.1 μ V

Technical field

The present invention relates to instrument that DC voltage is measured.

Background technology

Current for the potential difference meter that four measurement disks is arranged, in the connection between the four measurement disks, telophragma generally adopts switch to switch, and so just produces the variation of contact resistance, brings restriction to resolution.In order to overcome this problem, generally adopt big brush with the increase contact area, and adopt silver-carbon/carbon-copper composite material; Application number 20051006223.1 discloses the new method that the potential difference meter that four measurement disks is arranged solves the switch contact resistance variation, its first, each is made up of second step disc measuring disk and replacement dish, measuring disk is identical with resistance on the replacement dish, resistance of the every increase of measuring disk, the replacement dish just reduces same resistance, its the 3rd, the 4th step disc respectively has measuring disk, replacement dish and bracket panel are formed, because the 3rd step disc was declined at 10 o'clock, the total resistance of circuit changed when the 4th step disc was put different indicating value, the 3rd step disc was put at 10 o'clock, the total resistance of circuit was constant when the 4th step disc was put different indicating value, the 3rd step disc removes for this reason measuring disk, outside the replacement dish, increased bracket panel distinguish step disc put 10 and the circuit of declining 10 two kinds of situations connect, the 4th step disc has also increased bracket panel, has 10 resistance to insert or cut out several resistance respectively above and makes the total resistance of circuit constant.Four measurement disks is connected two and measures between terminal, and the brush on the step disc switch is got rid of outside the measurement loop, does not exist switch to switch between the resistance on the four measurement disks, does not also just produce variation; Because 15 ° of angles are rotated in each stepping of potential difference meter step disc switch, every layer of 24 contact that can distribute, the measuring disk of first step disc and replacement dish are 21 contacts, two-layer inside and outside needing, every layer all has resistance, and internal layer resistance is overproof makes troubles to maintenance, the measuring disk of the 4th step disc, replacement dish and each half storey of bracket panel, the step disc switch also needs inside and outside two-layer, and internal layer also has resistance, and maintenance is also inconvenient.

Summary of the invention

A kind of minimum step that the objective of the invention is to design four measurement disks is the voltage-measuring equipment of 0.1 μ V, in the connection of four measurement disks, do not switch by switch, and first step disc cancellation replacement dish, and make four resistance on the step disc can both be contained in one deck.

Technical scheme of the present invention is taked like this: from the positive pole of voltage-measuring equipment 3V working power through the resistance measurement network formed by the resistance on four step discs, range transfer resistance and range selector setting resistance R to 509 Ω _NAnd the lockable adjustable resistance R of 0～1 Ω _P3, again through 10 * 22 Ω adjustable resistance R _P1And 0～25 Ω adjustable resistance R _P2Get back to the negative pole of working power and form voltage-measuring equipment work loop; Standard cell E _NAnodal through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂To setting up resistance R _NAnd lockable adjustable resistance R _P3, process 75K Ω current-limiting resistance R is to standard cell E again _NNegative pole is formed the voltage-measuring equipment standard loop; Be used to connect measured " U _X" two terminals, anodal terminal is through behind the resistor network of four measurement disks, again through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂Form the voltage-measuring equipment equalizing network to the negative pole terminal; First step disc has measuring disk I, it has 0,1,2 ... 22 totally 23 gears, except that between 0,1 contact, directly connecting, connect one of 10 Ω resistance between all the other each grade contacts, other has bracket panel I ' and bracket panel I ", the brush of bracket panel I ' and bracket panel I " brush be connected with lead, tie point is circuit node B, bracket panel I ' and bracket panel I " 0 contact isolated, all the other all contacts connect with lead; Second step disc is made up of measuring disk II and bracket panel II ', measuring disk II has 0,1,2 ... 10 totally 11 gears have the resistance of 99 Ω to connect into ring-type: the 1st resistance R above 0～8 gear ₁One end welds the 2nd resistance R ₂One end, resistance R ₂The other end welds the 3rd resistance R ₃One end ... welding successively, the 8th resistance R ₈The other end and the 9th resistance R ₉An end tie point be circuit node H, the 9th resistance R ₉The other end and the 1st resistance R ₁The other end and being connected of 0 contact of the 3rd dish measuring disk, 0 contact of the 3rd dish measuring disk is circuit node D, resistance R ₁With resistance R ₂Tie point be connected resistance R through 12 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 6 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 2 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R with the 4th contact ₅With resistance R ₆Tie point be connected resistance R with the 5th contact ₆With resistance R ₇Tie point be connected resistance R through 2 Ω resistance with the 6th contact ₇With resistance R ₈Tie point be connected resistance R through 6 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be that node H one tunnel is connected with the 8th contact through 12 Ω resistance, another road is connected with the 9th contact through 11 Ω resistance to node F after through 1 Ω resistance again, node F through 1 Ω resistance to node C, node C is connected with the 10th contact through 10 Ω resistance, " 0 " contact of measuring disk II is connected with node D through 20 Ω resistance, is the resistance of 10 * 0.5 Ω on the bracket panel II ' of second step disc; The 3rd step disc is made up of measuring disk III that is both 10 * 1 Ω and replacement dish III ', and the brush of the brush of measuring disk III and replacement dish III ' is with a slice metallic brush sheet; The 4th step disc has only measuring disk IV, and the corresponding contact on its each contact and the measuring disk III connects; Bracket panel II ' the 10th contact and 100 Ω resistance R ₁₇An end be parallel to node A, node A connects the positive pole of voltage-measuring equipment 3V working power, 100 Ω resistance R ₁₇The other end connect range selector K ₁Middle K _1-1Layer * 0.1, * 1 range contact, 0 contact of bracket panel II ' connects bracket panel I " 0 contact, the brush of bracket panel II ' connects bracket panel I " other contact except that 0 contact, the brush of measuring disk II is through 200 Ω resistance R ₁₂The back connects the brush and bracket panel I of bracket panel I ' " the Node B that is connected of brush; other contacts connection measuring disk I 22nd contact of bracket panel I ' except that 0 contact; measuring disk I the 0th, 1 contact is connected with node C; 0 contact of bracket panel I ' is connected with node D after through 220 Ω resistance, the brush of the measuring disk IV 100k Ω resistance R of connecting ₁₅Back and 284.725 Ω resistance R ₁₆The tie point of one end is circuit node E, the 10th the series connection 9995 Ω resistance R of replacement dish III ' ₁₄Back connected node E, 529.392 Ω resistance R ₁₃One end connected node D, other end connected node E, 284.725 Ω resistance R ₁₆The other end be connected in range selector K ₁Middle K _1-1Layer * 10 range contacts, K _1-1Layer * 10 range contacts and range selector K ₁Middle K _1-2Layer * 1 range contact connects K with lead _1-2Layer * 1 range contact is through 9000 Ω resistance R ₁₈Back and K _1-2Layer * 0.1 range contact connects range selector K ₁Middle K _1-3Layer * 10 range contacts connect the setting resistance R _NNoble potential one end, range selector K ₁Middle K _1-3Layer * 1 range contact is through 810 Ω resistance R ₁₉Back and setting resistance R _NNoble potential one end connects, range selector K ₁Middle K _1-3Layer * 0.1 range contact is through 801 Ω resistance R ₂₀Back and setting resistance R _NNoble potential one end connects, and is used to connect measured " U _X" two measure terminal, anodally be connected with measuring disk I brush, negative pole passes through double-point double-throw switch K ₂The back is connected with the 10th of measuring disk III.

By above technical scheme, first step disc need not the replacement dish, does not all have resistance on the two-layer bracket panel, can be contained in the switch nexine, and measuring disk I is contained in the switch skin; Second step disc need not the replacement dish, 15 ° of angles are rotated in each stepping of switch, each 11 contact of the bracket panel II ' of second step disc and measuring disk II are distributed in same one deck of switch, resistance is contained in the switch skin, three, the 4th step disc does not all have bracket panel, resistance can be contained in the switch skin, unloads when resistance is overproof and loads onto easily, and this brings convenience for debugging and maintenance; This makes voltage-measuring equipment simple in structure, and volume-diminished has also reduced production cost; On the total circuit partly in voltage-measuring equipment internal compensation loop and work loop, there is not switch, so there is not variation influence, when the reset of voltage-measuring equipment four measurement disks, the zero potential of voltage-measuring equipment is the zero potential that D is ordered, in equalizing network, do not exist working current to flow through lead resistance, so this voltage-measuring equipment zero potential is very little, owing on the total circuit partly in voltage-measuring equipment internal compensation loop and work loop, do not have switch to switch, so this voltage-measuring equipment thermoelectrical potential and variable thermoelectrical potential are also very little.

Description of drawings

Accompanying drawing is a principle of the invention circuit.

Embodiment

Among the figure, measuring disk II has 9 the 9 end to end resistance rings of Ω between 1～8 contact, when measuring disk II puts " 4 ", " 5 ", the brush of measuring disk II is to being that 59 Ω resistance are in parallel with 49 Ω resistance between the node D, back in parallel resistance is 20 Ω to the maximum, other contact of measuring disk II all will be connected to 20 Ω to the resistance between the node D, and corresponding point directly are connected on " 4 ", " 5 " contact and the resistance ring; When measuring disk II put " 3 " or puts " 6 ", the brush of measuring disk II was to being that 39 Ω resistance are in parallel with 69 Ω resistance between the node D, and back in parallel resistance is 18 Ω, so 3,6 contacts are connected with corresponding point on the resistance ring through 2 Ω resistance; When measuring disk II put " 2 " or puts " 7 ", the brush of measuring disk II was to being that 29 Ω resistance are in parallel with 79 Ω resistance between the node D, and back in parallel resistance is 14 Ω, so 2,7 contacts are connected with corresponding point on the resistance ring through 6 Ω resistance; When measuring disk II set or when putting " 8 ", the brush of measuring disk II is to being that 19 Ω resistance is in parallel with 89 Ω resistance between the node D, and back in parallel resistance is 8 Ω, so 1,8 contacts are connected with corresponding point on the resistance ring through 12 Ω resistance; When measuring disk II puts " 9 ", the brush of measuring disk II is to being that 11 Ω resistance add 1 Ω resistance and add that 8 Ω connect into 20 Ω resistance on the resistance ring again between the node D, when measuring disk II put " 10 ", the brush of measuring disk II was to being that 10 Ω resistance add 2 Ω resistance and add that 8 Ω connect into 20 Ω resistance on the resistance ring again between the node D.When measuring disk II reset, the brush of measuring disk II is to being that 20 Ω resistance connect between the node D,

The first step disc reset, second step disc are put " n " (n=0,1,2,3 ... 9,10) time, the brush of bracket panel I ' is that two resistance that are both 220 Ω are in parallel with resistance value between the node D, is 110 Ω therefore.

First step disc is put " n " (n=0,1,2,3 ... 22), during the second step disc reset, the brush of bracket panel I ' is that two resistance that are both 220 Ω are in parallel with resistance value between the node D, is 110 Ω therefore.

When first, second step disc during not reset, the calculating of the resistance value between the brush of bracket panel I ' and the node D removes second step disc and puts outside " 8,9,10 ", all needs to carry out triangle-star conversion.

During the second step disc set, the calculating of resistance value between the brush of bracket panel I ' and the node D: establish resistance (R ₂+ R ₃+ ... + R ₈) and resistance R ₉The both sides resistance is equivalent to resistance r ₁, resistance R ₉With resistance R ₁The both sides resistance is equivalent to resistance r ₁' resistance (R ₂+ R ₃+ ... + R ₈) and resistance R ₁The both sides resistance is equivalent to resistance r ₁", be equivalent to resistance r ₁, r ₁', r ₁" intersection point is Q ₁:

R then ₁=(R ₂+ R ₃+ ... + R ₈) * R ₉/ (R ₁+ R ₂+ ... + R ₉)=7 * 9 * 9/9 * 9 Ω=7 Ω

r ₁’＝R ₁×R ₉/(R ₁+R ₂+…+R ₉)＝9×9/9×9Ω＝1Ω

r ₁”＝(R ₂+R ₃+…+R ₉)×R ₁/(R ₁+R ₂+…+R ₉)＝7×9×9/9×9Ω＝7Ω

Resistance value equals (212 Ω+r between the brush of bracket panel I ' and the node D ₁) * (212 Ω+r ₁")/(2 * 219) Ω+r ₁'=219 Ω/2+1 Ω=109.5 Ω+1 Ω=110.5 Ω

When second step disc is put " 2 ", the calculating of resistance value between the brush of bracket panel I ' and the node D: establish resistance (R ₃+ R ₄+ ... + R ₈) and resistance R ₉The both sides resistance is equivalent to resistance r ₂, resistance R ₉With resistance (R ₁+ R ₂) the both sides resistance is equivalent to resistance r ₂' resistance (R ₃+ R ₄+ ... + R ₈) and resistance (R ₁+ R ₂) the both sides resistance is equivalent to resistance r ₂", be equivalent to resistance r ₂, r ₂', r ₂" intersection point is Q ₂:

R then ₂=6 Ω r ₂'=2 Ω r ₂"=12 Ω

Resistance value equals (212 Ω+r between the brush of bracket panel II ' and the node D ₂) * (200 Ω+6 Ω+r ₂")/(2 * 218) Ω+r ₂'=218 Ω/2+2 Ω=109 Ω+2 Ω=111 Ω.

In like manner, when second step disc was put " 3 ", resistance value was 111.5 Ω between the brush of bracket panel I ' and the node D,

When second step disc was put " 4 ", resistance value was 112 Ω between the brush of bracket panel I ' and the node D,

When second step disc was put " 5 ", resistance value was 112.5 Ω between the brush of bracket panel I ' and the node D,

When second step disc was put " 9 ", resistance value was (211/2+9) Ω=114.5 Ω between the brush of bracket panel I ' and the node D, and when second step disc was put " 10 ", resistance value was (210/2+10) Ω=115 Ω between the brush of bracket panel I ' and the node D.Because the every stepping of measuring disk II increases by 0.5 Ω, so the every stepping of bracket panel II ' reduces by 0.5 Ω, makes the total resistance of circuit constant.

When the first or second step disc reset, the resistance value between the brush of bracket panel I ' and the node D is 110 Ω, and 10 * 0.5 Ω resistance of bracket panel II ' all enter circuit, and making the resistance value between node A and the node D is that 115 Ω remain unchanged.

When three, the 4th step disc was put different indicating value, the resistance between node D and node E changed between 500.2728 Ω～500.2780 Ω, and node E connects 284.725 Ω resistance R ₁₆After, pass through node D to K switch from node A ₁Middle K _1-1Layer * resistance value between 1 range contact is 900 Ω, and the change in resistance of 0.005 Ω is 6/1000000ths to the relative variation of 900 Ω, and influence can be ignored.

Electric current is 2mA during the standardization of voltage-measuring equipment working current, and when * 10 ranges, the 2mA electric current passes through node D to K switch from node A ₁Middle K _1-1* 10 range contacts, 100 Ω resistance R ₁₇There is not partial current.

At * 10 ranges, the 2mA electric current flows through the 10th the process Node B of bracket panel II ' to node D, and measuring disk II puts " n " [n=1,2,3 ... 8 (r ₈=0) in the time of], I is to being equivalent to resistance r for Node B process measuring disk _n, r _n', r _n" intersection point Q _n(n=1,2,3 ... 8) with through 200 Ω resistance R ₁₂To intersection point Q _nResistance value equates that when measuring disk II put " 9 ", I was to the resistance value of node F and through 200 Ω resistance R for Node B process measuring disk ₁₂Resistance value to node F all equals 211 Ω, so flow through measuring disk I and 200 Ω resistance R ₁₂Electric current respectively be 1mA, when measuring disk II puts " 10 ", Node B through measuring disk I to the resistance value of node C and through 200 Ω resistance R ₁₂Resistance value to node C all equals 210 Ω, so flow through measuring disk I and 200 Ω resistance R ₁₂Electric current also respectively be 1mA.

For 9 the 9 Ω end to end resistance rings of measuring disk II between 1～8 contact, resistance R during measuring disk II set ₁To be all 9 Ω resistance in parallel with 8 resistances, flows through resistance R ₉Electric current be 1/9mA, the voltage U between node H and the node D _HD=1/9 * 9mV=1mV; Resistance (R when measuring disk II puts " 2 " ₁+ R ₂) to be all 9 Ω resistance in parallel with 7 resistances, flows through resistance R ₉Electric current be 2/9mA, the voltage U between node H and the node D _HD=2/9 * 9mV=2mV; (n=1,2,3 when in like manner, measuring disk II puts " n " ... 8) voltage U between resistance nodes H and the node D _HD=nmV; When measuring disk II puts " 9 ", the voltage U between node F and the node D on the 8 Ω resistance rings _HD=8mV adds 1 Ω resistance R ₁₀Last 1mV, 9mV altogether; When measuring disk II puts " 10 ", the voltage U between node C and the node D on the 8 Ω resistance rings _HD=8mV adds 1 Ω resistance R ₁₀Last 1mV and 1 Ω resistance R ₁₁Last 1mV, 10mV altogether; When measuring disk I and measuring disk II reset, electric current is without resistance R ₉, U _CD=0mV; The electric current that flows through measuring disk I when not reset of measuring disk I is superimposed upon on the measuring disk II at the 10mV voltage between node C, the D, replaces the resistance between 0,1 contact among the measuring disk I.

Voltage-measuring equipment 2mA working current is divided into three the tunnel: the one tunnel through measuring disk IV through first, second step disc behind node D, another road is through replacement dish III ', and one the tunnel through 529.392 Ω resistance R again ₁₃, three road electric currents meet at node E.When three, the 4th step disc is put different indicating value between node D and the node E resistance change, three, resistance minimum between node D and node E during the 4th step disc reset indicating value, resistance maximum between node D and node E when three, the 4th step disc is put " 10 " indicating value, get intermediate value, resistance is not having resistance R between node D and the node E when the 3rd, the 4th step disc is put " 5 " indicating value for this reason ₁₃When in parallel is (10 ⁵÷ 11+5) Ω is 0.11mA in order to make the total current that flows through the 3rd, the 4th step disc, with 529.392 Ω resistance R ₁₃The electric current of shunting 1.89mA; Three, during the 4th step disc reset indicating value, the total current that flows through the 3rd, the 4th step disc is 0.11001mA, and when the 3rd, the 4th step disc was put " 10 " indicating value, the total current that flows through the 3rd, the 4th step disc was 0.10999mA, error is ten thousand/, influence can be ignored; Flow through resistance R ₁₄With resistance R ₁₅The current ratio exact value be 10, when the 3rd, the 4th step disc reset indicating value, flow through resistance R ₁₄With resistance R ₁₅Current ratio be 9.995, when the 3rd, the 4th step disc is put " 10 " indicating value, flow through resistance R ₁₄With resistance R ₁₅Current ratio be 10.005, error is 5/10000ths owing to be last two dishes, influence also can be ignored; Therefore, indicating value of the every increase of the 3rd step disc, the voltage between node D and the node E increases 0.1mV, indicating value of the every increase of the 4th step disc, the voltage between node D and the node E increases 0.01mV.

During the working current standardization, first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U at this moment _x" two measure that voltage is between terminal:

U _x＝10n ₁+n ₂+0.1n ₃+0.01n ₄(mV)

When * 1 range, pass through node D to K switch from node A _1-2* 900 Ω resistance and 100 Ω resistance R between 1 range contact ₁₇Parallel connection, the electric current that therefore flows through bracket panel II ' is 0.2mA, flows through resistance R ₁₇Electric current be 1.8mA, the resistance that parallel connection reduces by the series connection 810 Ω resistance R ₁₉Come the holding circuit resistance constant.At this moment first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U _x" two measure that voltage is between terminal:

U _x＝1n ₁+0.1n ₂+0.01n ₃+0.001n ₄(mV)

When * 0.1 range, pass through node D to K switch from node A _1-2* 900 Ω resistance between the 0.1 range contact 9000 Ω resistance R of connecting ₁₈After 9900 Ω resistance values and 100 Ω resistance R are arranged ₁₇Parallel connection is a resistance R ₁₇99 times, the electric current that therefore flows through bracket panel II ' is 0.02mA, flows through resistance R ₁₇Electric current be 1.98mA, the resistance that parallel connection reduces by the series connection 801 Ω resistance R ₂₀Come the holding circuit resistance constant.At this moment first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U _x" two measure that voltage is between terminal:

U _x＝0.1n ₁+0.01n ₂+0.001n ₃+0.0001n ₄(mV)

Because the electromotive force of standard cell disperses, between 1.0188V～1.0196V, standardized working current is 2mA, therefore sets up resistance R _NGet 509 Ω, add the lockable adjustable resistance R of 0～1 Ω _P3, variation range that can the coverage criteria cell emf.

Node A is to setting up resistance R _NThe resistance of noble potential one end is 900 Ω, the setting resistance R of 509 Ω _NWith 0～1 Ω adjustable resistance R _P3Be 510 Ω, amount to 1410 Ω, bear about 2.82V voltage; Voltage-measuring equipment adopts two groups of dry cell power supplies, and electromotive force was about 1.65V when dry cell was new, has used the electric current shakiness old, can both make the working current of voltage-measuring equipment be adjusted to standardization in order to make dry cell under new, former affection condition, for this reason, gets adjustable resistance R _P1Be 10 * 22 Ω, adjustable resistance R _P2Be 0～25 Ω, dry cell voltage usable range is between 2.82V～3.31V.

The normalized current of voltage-measuring equipment is such acquisition: 200mV standard signal voltage is pressed polarity and voltage-measuring equipment " U _x" two measure terminal and connect, the total indicating value of each step disc of voltage-measuring equipment is identical with the standard signal magnitude of voltage, double-point double-throw switch K ₂Throw to the left side, regulate adjustable resistance R _P1And adjustable resistance R _P2, make galvanometer G nulling; Again with double-point double-throw switch K ₂Throw to the right, regulate adjustable resistance R _P3, make galvanometer G nulling, repeat once again after, adjustable resistance R _P3Locking, at this moment the working current of voltage-measuring equipment is with regard to standardization.

Claims

A kind of minimum step is the voltage-measuring equipment of 0.1 μ V, from the positive pole of voltage-measuring equipment 3V working power through the resistance measurement network formed by the resistance on four step discs, range transfer resistance and range selector setting resistance R to 509 Ω _NAnd the lockable adjustable resistance R of 0～1 Ω _P3, again through 10 * 22 Ω adjustable resistance R _P1And 0～25 Ω adjustable resistance R _P2Get back to the negative pole of working power and form voltage-measuring equipment work loop; Standard cell E _NAnodal through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂To setting up resistance R _NAnd lockable adjustable resistance R _P3, process 75K Ω current-limiting resistance R is to standard cell E again _NNegative pole is formed the voltage-measuring equipment standard loop; Be used to connect measured " U _X" two terminals, anodal terminal is through behind the resistor network of four measurement disks, again through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂Form the voltage-measuring equipment equalizing network to the negative pole terminal; It is characterized in that first step disc has measuring disk I, it has 0,1,2 ... 22 totally 23 gears, except that between 0,1 contact, directly connecting, connect one of 10 Ω resistance between all the other each grade contacts, other has bracket panel I ' and bracket panel I ", the brush of bracket panel I ' and bracket panel I " brush be connected with lead, tie point is circuit node B, bracket panel I ' and bracket panel I " 0 contact isolated, all the other all contacts connect with lead; Second step disc is made up of measuring disk II and bracket panel II ', measuring disk II has 0,1,2 ... 10 totally 11 gears have the resistance of 99 Ω to connect into ring-type: the 1st resistance R above 0～8 gear ₁One end welds the 2nd resistance R ₂One end, resistance R ₂The other end welds the 3rd resistance R ₃One end ... welding successively, the 8th resistance R ₈The other end and the 9th resistance R ₉An end tie point be circuit node H, the 9th resistance R ₉The other end and the 1st resistance R ₁The other end and being connected of 0 contact of the 3rd dish measuring disk, 0 contact of the 3rd dish measuring disk is circuit node D, resistance R ₁With resistance R ₂Tie point be connected resistance R through 12 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 6 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 2 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R with the 4th contact ₅With resistance R ₆Tie point be connected resistance R with the 5th contact ₆With resistance R ₇Tie point be connected resistance R through 2 Ω resistance with the 6th contact ₇With resistance R ₈Tie point be connected resistance R through 6 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be that node H one tunnel is connected with the 8th contact through 12 Ω resistance, another road is connected with the 9th contact through 11 Ω resistance to node F after through 1 Ω resistance again, node F through 1 Ω resistance to node C, node C is connected with the 10th contact through 10 Ω resistance, " 0 " contact of measuring disk II is connected with node D through 20 Ω resistance, is the resistance of 10 * 0.5 Ω on the bracket panel II ' of second step disc; The 3rd step disc is made up of measuring disk III that is both 10 * 1 Ω and replacement dish III ', and the brush of the brush of measuring disk III and replacement dish III ' is with a slice metallic brush sheet; The 4th step disc has only measuring disk IV, and the corresponding contact on its each contact and the measuring disk III connects; Bracket panel II ' the 10th contact and 100 Ω resistance R ₁₇An end be parallel to node A, node A connects the positive pole of voltage-measuring equipment 3V working power, 100 Ω resistance R ₁₇The other end connect range selector K ₁Middle K _1-1Layer * 0.1, * 1 range contact, 0 contact of bracket panel II ' connects bracket panel I " 0 contact, the brush of bracket panel II ' connects bracket panel I " other contact except that 0 contact, the brush of measuring disk II is through 200 Ω resistance R ₁₂The back connects the brush and bracket panel I of bracket panel I ' " the Node B that is connected of brush; other contacts connection measuring disk I 22nd contact of bracket panel I ' except that 0 contact; measuring disk I the 0th, 1 contact is connected with node C; 0 contact of bracket panel I ' is connected with node D after through 220 Ω resistance, the brush of the measuring disk IV 100k Ω resistance R of connecting ₁₅Back and 284.725 Ω resistance R ₁₆The tie point of one end is circuit node E, the 10th the series connection 9995 Ω resistance R of replacement dish III ' ₁₄Back connected node E, 529.392 Ω resistance R ₁₃One end connected node D, other end connected node E, 284.725 Ω resistance R ₁₆The other end be connected in range selector K ₁Middle K _1-1Layer * 10 range contacts, K _1-1Layer * 10 range contacts and range selector K ₁Middle K _1-2Layer * 1 range contact connects K with lead _1-2Layer * 1 range contact is through 9000 Ω resistance R ₁₈Back and K _1-2Layer * 0.1 range contact connects range selector K ₁Middle K _1-3Layer * 10 range contacts connect the setting resistance R _NNoble potential one end, range selector K ₁Middle K _1-3Layer * 1 range contact is through 810 Ω resistance R ₁₉Back and setting resistance R _NNoble potential one end connects, range selector K ₁Middle K _1-3Layer * 0.1 range contact is through 801 Ω resistance R ₂₀Back and setting resistance R _NNoble potential one end connects, and is used to connect measured " U _X" two measure terminal, anodally be connected with measuring disk I brush, negative pole passes through double-point double-throw switch K ₂The back is connected with the 10th of measuring disk III.